The objective of this project is to define the extent and mechanisms by which the cell cycle in certain human and experimental malignant cells (namely glial and squamous bronchogenic carcinoma) is mobilized into S phase by coumadin derivatives, particularly racemic sodium warfarin. Ongoing work in our laboratory has established that the in vitro cell cycle traverse of these neoplasms is remarkably sensitive to very low concentrations of warfarin. In view of apparant therapeutic synergy witnessed in humans receiving warfarin therapy in conjunction with irradiation and 5-flourouracil, particularly in cases of squamous carcinoma metastatic to brain, these observations merit urgent investigation.